nn = 200200
P = 10 ** 9 + 7

fa = [1] * (nn+1)
fainv = [1] * (nn+1)
for i in range(nn):
    fa[i+1] = fa[i] * (i+1) % P
fainv[-1] = pow(fa[-1], P-2, P)
for i in range(nn)[::-1]:
    fainv[i] = fainv[i+1] * (i+1) % P

N, K = map(int, input().split())
A = [int(a) for a in input().split()]

X = [1]
for i in range(1, 200100):
    X.append(X[-1] * (K + i) % P * fainv[i] % P * fa[i-1] % P)

ans = 0
for i, a in enumerate(A):
    ans = (ans + a * X[i] % P* X[N - i - 1]) % P

print(ans)